Robert
I don't know the USA models so well, but it certainly
sounds as though the cassette carriage is damaged on
the HF300. Parts are virtually impossible to obtain, the
only hope is to get a scrap machine with a good front
loading mechanism and swap it over. Other models will
use essentially the same mechanism. This looks similar
to the UK model SL-HF100, but others will be the same
too.
The Sears one could be anything, I don't recognise that
one at all. If it's a Sanyo it may only need a service
kit (I supply them for some models). Have a look inside
it and compare it to the pictures on my web site:
http://www.colin99.co.uk/extras/reelidler/how_to_service_a_sanyo_beta.htm
See if it looks familiar.
If not, look at the palsite and see which UK model looks
most like the Sears one, and we can go from there:
http://www.palsite.com/models.html
Regards,
Colin
www.video99.co.uk